如果你特别想为uibutton定制圆角，有很多不同的方法来实现。

下面的代码示例(感谢Erica)很好地概述了所有可能性。

iOS 15之前的圆角按钮

在iOS 15之前，你可以通过设置图层来制作圆角按钮。cornerRadius, backgroundColor和setTitleColor。

let button = UIButton(type: .system)
button.setTitle("Button", for: .normal)
button.setTitleColor(.white, for: .normal)
button.backgroundColor = .systemPink
button.layer.cornerRadius = 8

button.contentEdgeInsets = UIEdgeInsets(
  top: 10,
  left: 20,
  bottom: 10,
  right: 20
)

胶囊按钮

如果我们增加足够大的角半径值，您可以创建一个胶囊风格的按钮。为了创建一个胶囊风格的按钮，我们设置角半径等于按钮高度的一半。由于按钮的高度可能会根据标题大小或布局而变化，我通常为胶囊样式创建一个UIButton子类。

class CapsuleButton: UIButton {
  override func layoutSubviews() {
    super.layoutSubviews()
    let height = bounds.height
    layer.cornerRadius = height/2
  }
}

let capsule = CapsuleButton(type: .system)
capsule.setTitle("Button", for: .normal)
capsule.setTitleColor(.white, for: .normal)
capsule.backgroundColor = .systemPink
capsule.contentEdgeInsets = UIEdgeInsets(
  top: 10,
  left: 20,
  bottom: 10,
  right: 20
)

光滑的角落

如果你想复制苹果平滑角，你也可以用拐角曲线属性来做。要创建连续的平滑角，请设置图层。按钮连续的曲线。

let button = UIButton(type: .system)
button.setTitle("Button", for: .normal)
button.setTitleColor(.white, for: .normal)
button.backgroundColor = .systemPink
button.layer.cornerRadius = 8
button.layer.cornerCurve = .continuous

button.contentEdgeInsets = UIEdgeInsets(
  top: 10,
  left: 20,
  bottom: 10,
  right: 20
)

圆角按钮在iOS 15使用UIButton。配置

在iOS 15中，苹果引入了一种通过UIButton.Configuration自定义按钮的新方法。

var configuration = UIButton.Configuration.filled()

configuration.title = "Button"
configuration.baseBackgroundColor = UIColor.systemPink
configuration.contentInsets = NSDirectionalEdgeInsets(
  top: 10,
  leading: 20,
  bottom: 10,
  trailing: 20
)

let button = UIButton(configuration: configuration, primaryAction: nil)

使用cornerStyle控制角的半径

UIButton。配置有许多内置的角样式供您选择。你可以用cornerStyle属性来设置。

configuration.cornerStyle = .small
configuration.cornerStyle = .medium
configuration.cornerStyle = .large
configuration.cornerStyle = .capsule

自定义角半径

如果你想要一些更独特的东西，你可以通过UIBackgroundConfiguration的cornerRadius指定角的半径。

var configuration = UIButton.Configuration.filled()
configuration.title = "Button"
configuration.baseBackgroundColor = UIColor.systemPink
configuration.contentInsets = NSDirectionalEdgeInsets(
  top: 10,
  leading: 20,
  bottom: 10,
  trailing: 20
)
configuration.background.cornerRadius = 20

configuration.cornerStyle = .fixed


let button = UIButton(configuration: configuration, primaryAction: nil)

下面的方法最适合我 (这段代码位于UIView扩展中，因此self表示一些我们必须添加阴影和圆角的UIView)

- (void)addShadowViewWithCornerRadius:(CGFloat)radius {

UIView *container = self.superview;

if (!container) {
    return;
}

UIView *shadowView = [[UIView alloc] init];
shadowView.translatesAutoresizingMaskIntoConstraints = NO;
shadowView.backgroundColor = [UIColor lightGrayColor];
shadowView.layer.cornerRadius = radius;
shadowView.layer.masksToBounds = YES;

[container addSubview:shadowView];
[container bringSubviewToFront:shadowView];

[container addConstraint:[NSLayoutConstraint constraintWithItem:shadowView
                                                      attribute:NSLayoutAttributeWidth
                                                      relatedBy:NSLayoutRelationEqual
                                                         toItem:self
                                                      attribute:NSLayoutAttributeWidth
                                                     multiplier:1.0
                                                       constant:0.0]];
[container addConstraint:[NSLayoutConstraint constraintWithItem:shadowView
                                                      attribute:NSLayoutAttributeLeading
                                                      relatedBy:NSLayoutRelationEqual
                                                         toItem:self
                                                      attribute:NSLayoutAttributeLeading
                                                     multiplier:1.0
                                                       constant:2.0]];

[container addConstraint:[NSLayoutConstraint constraintWithItem:shadowView
                                                      attribute:NSLayoutAttributeHeight
                                                      relatedBy:NSLayoutRelationEqual
                                                         toItem:self
                                                      attribute:NSLayoutAttributeHeight
                                                     multiplier:1.0
                                                       constant:0.0]];
[container addConstraint:[NSLayoutConstraint constraintWithItem:shadowView
                                                      attribute:NSLayoutAttributeTop
                                                      relatedBy:NSLayoutRelationEqual
                                                         toItem:self
                                                      attribute:NSLayoutAttributeTop
                                                     multiplier:1.0
                                                       constant:2.0]];
[container sendSubviewToBack:shadowView];
}

此代码与其他代码示例之间的主要区别在于，它将阴影视图添加为兄弟视图(而不是将当前视图添加为阴影视图的子视图)，从而消除了以任何方式修改现有视图层次结构的需要。

阴影+边界+角半径

    scrollview.backgroundColor = [UIColor whiteColor]; 
    CALayer *ScrlViewLayer = [scrollview layer];
    [ScrlViewLayer setMasksToBounds:NO ];
    [ScrlViewLayer setShadowColor:[[UIColor lightGrayColor] CGColor]];
    [ScrlViewLayer setShadowOpacity:1.0 ];
    [ScrlViewLayer setShadowRadius:6.0 ];
    [ScrlViewLayer setShadowOffset:CGSizeMake( 0 , 0 )];
    [ScrlViewLayer setShouldRasterize:YES];
    [ScrlViewLayer setCornerRadius:5.0];
    [ScrlViewLayer setBorderColor:[UIColor lightGrayColor].CGColor];
    [ScrlViewLayer setBorderWidth:1.0];
    [ScrlViewLayer setShadowPath:[UIBezierPath bezierPathWithRect:scrollview.bounds].CGPath];

在研究了一整天的圆角视图与阴影之后，我很高兴在这里发布我的自定义uiview类，希望结束这个问题:

RoundCornerShadowView.h

#import <UIKit/UIKit.h>

@interface RoundCornerShadowView : UIView

@end

RoundCornerShadowView.m

#import "RoundCornerShadowView.h"

@implementation RoundCornerShadowView

// *** must override this method, not the other method ***
// otherwise, the background corner doesn't disappear....
// @2015/05/29
-(void) layoutSubviews {
    [super layoutSubviews];//is must to ensure rightly layout children view

    //1. first, create Inner layer with content
    CALayer *innerView = [CALayer layer];
    innerView.frame = CGRectMake(0,0,self.bounds.size.width,self.bounds.size.height);
    //instead of: innerView.frame = self.frame;
    innerView.borderWidth = 1.0f;
    innerView.cornerRadius = 6.0f;
    innerView.masksToBounds = YES;
    innerView.borderColor = [[UIColor lightGrayColor] CGColor];
    innerView.backgroundColor = [[UIColor whiteColor] CGColor];
    //put the layer to the BOTTOM of layers is also a MUST step...
    //otherwise this layer will overlay the sub uiviews in current uiview...
    [self.layer insertSublayer:innerView atIndex:0];

    //2. then, create shadow with self layer
    self.layer.masksToBounds = NO;
    self.layer.shadowColor = [[UIColor darkGrayColor] CGColor];
    self.layer.shadowOpacity = 0.4f;
    //shadow length
    self.layer.shadowRadius = 2.0f;
    //no offset
    self.layer.shadowOffset = CGSizeMake(0, 0);
    //right down shadow
    //[self.layer setShadowOffset: CGSizeMake(1.0f, 1.0f)];

    //3. last but important, MUST clear current view background color, or the color will show in the corner!
    self.backgroundColor = [UIColor clearColor];
}

@end

所以，不需要在视图中添加子视图或在目标视图中添加子视图，只需在当前视图中添加一层，并执行3步即可完成!

仔细查看代码中的注释，这有助于理解组件!

使用Swift 4和Xcode 9，这是一个用投影和边框舍入ImageView的工作示例。

    //set dimensions and position of image (in this case, centered)
    let imageHeight: CGFloat = 150, imageWidth: CGFloat = 150
    let xPosition = (self.view.frame.width / 2) - (imageWidth / 2)
    let yPosition = (self.view.frame.height / 2) - (imageHeight / 2)

    //set desired corner radius
    let cornerRadius: CGFloat = 20

    //create container for the image
    let imageContainer = UIView(frame: CGRect(x: xPosition, y: yPosition, width: imageWidth, height: imageHeight))

    //configure the container
    imageContainer.clipsToBounds = false
    imageContainer.layer.shadowColor = UIColor.black.cgColor
    imageContainer.layer.shadowOpacity = 1
    imageContainer.layer.shadowOffset = CGSize(width: 3.0, height: 3.0)
    imageContainer.layer.shadowRadius = 5
    imageContainer.layer.shadowPath = UIBezierPath(roundedRect: imageContainer.bounds, cornerRadius: cornerRadius).cgPath

    //create imageView
    let imageView = UIImageView(frame: imageContainer.bounds)

    //configure the imageView
    imageView.clipsToBounds = true
    imageView.layer.cornerRadius = cornerRadius
    //add a border (if required)
    imageView.layer.borderColor = UIColor.black.cgColor
    imageView.layer.borderWidth = 1.0
    //set the image
    imageView.image = UIImage(named: "bird")

    //add the views to the superview
    view.addSubview(imageContainer)
    imageContainer.addSubview(imageView)

如果你想让图像是圆形的:(并且显示为无边框)

let cornerRadius = imageWidth / 2

当为容器视图分配阴影路径时，我使用以下技巧解决了这个问题:

[UIBezierPath bezierPathWithRoundedRect:cell.bounds cornerRadius:12]

请注意，阴影的路径是一个圆角矩形，与单元格包含的背景具有相同的角半径:

//this is the border for the UIView that is added to a cell
cell.backgroundView.layer.cornerRadius = 12;
cell.backgroundView.layer.masksToBounds = YES;
cell.backgroundView.layer.borderColor = [UIColor darkGrayColor].CGColor;
cell.backgroundView.layer.borderWidth = 1;

//this is the shadow around the cell itself (cannot have round corners with borders and shadow, need to use two views
cell.layer.shadowRadius = 2;
cell.layer.cornerRadius = 12;
cell.layer.masksToBounds = NO;
[[cell layer] setShadowColor:[[UIColor darkGrayColor] CGColor]];

[[cell layer] setShadowOffset:CGSizeMake(0.0,0.0)];
[[cell layer] setShadowOpacity:1.0];

UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:cell.bounds cornerRadius:12];
[[cell layer] setShadowPath:[path CGPath]];